High frequency dental tool



J. R. RICHARDS HIGH FREQUENCY DENTAL TOOL Feb. 24, 1959 Filed May 28.1954 INVENTOR MES R. RICHARDS .um r mw ATTORNEY United States Patent OHIGH FREQUENCY DENTAL TOUL `lames R. Richards, Cheverly, Md., assignerto the United States of America as represented by the Secretary of theNavy The invention described herein may be manufactured and used by orfor the Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

The present invention relates to a high frequency dental toolkand to aprocess of high frequency dental clinical wor An object of the inventionis the elimination of the slow, cumbersome, heat generating, inaccurateand painful dental drilling with the conventional rotating burr and theprovision of a smooth, rapid and efficient excavation method, having noobjectionable effects upon the patient and no shock-or-strain-effectsupon the tooth drilled.

Another object of the invention is to apply high frequency low amplitudeoscillations as the motive tooth excavation actuating power.

A further object of the invention is to employ in dental clinical workthe method of motivating abrasives in suspension at a high frequency andacceleration and low amplitude against the tooth under excavation.

Still another object of the inventionis a dental clinical instrumentcapable of packing a filling into a tooth excavation by high frequencyoscillations.

Another object of the invention is to provide a dental excavating toolmotivated by high frequency oscillations comprising its own liuidcooling supply and evacuation without damping the high frequencyoscillations of the tool.

Another object of the invention comprises the provision of an abrasiveand suspension supplying and evacuating means in the excavating tool.

A further object of the invention is to provide linger tip controls ofthe various supply and evacuation providing conduits, instantly andeasily operable during the clinical work and without any interruptions.

Still another object of the invention is the provision of a dental tool,embodying the tooth excavating and flling functions here described, andalso capable of accurate, easy performance in the limited working spaceof the mouth of the patient.

Another object of the invention is to provide a small light pencil-likedrill enabling the operator to operate it with an artists ease andfashion to excavate holes and channels of complex shapes with extremelyclose tolerances desirable for this type of work.

A further object of the invention is to use a premade inlay filling as atip extension of the dental tool herein described to preform anexcavation in the tooth, accurately fitting the inlay without thenecessity of any repeated trial and error drillings required up topresent.

Another object of the invention is to make it possible for the firsttime in dental industry to use premade dental inlays of fixed shapes andstandardized sizes in filling teeth cavities more efficiently and lessexpensively than known up to present.

Other objects and advantages of this invention will be- ICC comeapparent from the following description and accompanying drawings inwhich: y

Fig. l represents a longitudinal section ofthe high frequency dentaltool showing parts in elevation;

Fig. 2 is a perspective view of the magnetostrictive tube;

Fig. 3 shows a cross-section of the device taken on line 3-3 of Fig. l;

Fig. 4 shows elevations of modifications of the tip;

Fig. 5 is a diagrammatic view showing the valve con-v trois;

Fig. 6 exhibits elevations of' sample inlays correlated' with teeth tobe treated.

Referring now to the drawings like reference characters designate likeor corresponding parts throughout the severalgures.

The tool'is shown in Fig. 1 'as unit 10 and comprises:

in a preferred embodiment an 4outer tubular jacket 1-6 'of soft ironwith its working end closed by plastic cap 11 and its power inlet endclosed by plastic cap 12. Inside of the jacket is mounted a concentricmagnetostrictive nickel tube 13, over which at its nodal (center) pointis attachedV a brass sleeve 14, tightly fitting into the jacket, asshown in Fig. 3. The tube 13 is provided with longitudinal slots 15,shown in Fig. 2. In the space be tween the jacket and the tubeis a lowimpedance winding 17, shown in Fig. l in two layers wound over anonconductive spool 20. The spool as shown consists of two sections 20aand 20h, divided by and anchored with their inner ends in radial groovesof the sleeve 14.' The coil is wound uniformly over both sections, andFig. 1 shows the outer coil sections connected through slot 26e and theinner coil sections through slot 26d in the sleeve 14. This is shown inFigs. 1 and 3. The coil provides a magnetic field through an alternatingcur rent input 21, which may be controlled for instance by a finger tipcontrol switch or by a foot switch. Supported thjtkfi'tzdmlmagnet rings18 and 19 with air gaps between them and the tube. jacket, being madefor this purpose of a magnetic material such as soft iron, completes thepath of ux bc tween the two magnet rings and the tube. The perma-l nentmagnet rings provide the bias necessary to prevent a reversal of themagnetic flux. Without this bias the tube would become alternatelymagnetized to vibrate at twice the frequency of the sine wave applied.The magnetic field induced must not exceed the bias field. It has beendetermined empirically that for optimum performance of the embodiment ofthe invention shown in Fig. 1, the biasing flux density should be about60% of the saturation value, when appliedV at points of maximumamplitude. The magnetic bias may be provided for by other known meanssuch as a direct current without departure from the scope of theinvention. The magnetostriction causes the nickel tube 13 t0 expand andto contract longitudinally from the nodal point in both directions.Lateral expansions and contractions also occur simultaneously. Thelongitudinal slots 15 in tube 13, shown in Fig. 2 serve to reduce theeddy currents.

The amplitude of the magnetostriction depends on theV TheA mined asequal to thev evlmcpcityi of soundv propagationthrough'theparticillaletial used in the tube, divided byt'wo times thelength gfthetiibelmspeed of sound propagation in nickel being "16.320feet per second, the wave length at 25 kilocycles is 0.326'=3.9". Athigher frequencies the tube should be shortened, at lower frequenciesextended proportionally. A frequency at least above the audible rangewas selected to prevent undesirable noise productions, which couldaffect the patient adversely, however higher frequencies ofapproximately 25,000 cycles per second were found advantageous to themotivation of the present tool at approximately its 4" length with 50volts at 10 amperes. An acceleration of approximately 5,000gravitational units is necessary but Nof approximately 10,000gravitational unitsgis preferable to operate the present tool at higheiciency with an amplitude of about 0.01 mm. The double-layered coil 17in combination with the magnetic ux path comprised of the jacket 16 thepermanent magnet biasing rings 18 and 19 and the magneto-strictivenickel tube 13 serve as the generator of the tool tips reciprocatingoscillations in this embodiment when the coil is energized by aconventional power supply having the desired frequency and amplitudecharacteristics. To prevent damping of the tube 13 at its ends and toallow for free end movements of the tube, the tube is supported withinthe jacket only by its nodal support and the caps 11 and 12 are spacedfree of the tube to prevent any interference with the tubesmagnetostrictive movements. The working end of the tube freely protrudesthrough cap 11 and is provided with an end wall 31. The wall 3l is shownin Fig. 4a at an angle of 90 and in Fig. 4b at an angle of 135 from thetubes longitudinal extension 34. The closure 31 has a hole 32 connectingthe tubes interior 28 with the working area 33 of the tooth in thepatents mouth. The hole 32 therefore is strategically positioned foroptimum results close to the tip of the tube to permit a ow of thefluids from the tubes interior by gravitation and adhesion as shown inFig. 1. There may be several such holes 32 in the end wall, eachproviding an outlet for one or more interior conduit lines. One or morelines such as 23 and 24 may be connected from the outside of the jacket.The angle of 135 of the end wall with a tip of la" has been selected assufficient to provide a freedom of movement of the tool within thepatients mouth and simultaneously to permit the hole 32 to function as aconduit of water from area 28 by gravitation upon the tooth. A portionof the wall of the tube may taper off past the end wall 31 into aworking tip 34, as shown in Figs. 2 and 4c. When a changeable workingtip is desirable an alternative arrangement is to provide the workingend of the tube with means to fasten the tip to it, for instance bythread and screw, as shown in Fig. 4d or by soldering or welding. A kitof tips of various shapes and sizes may be made available for everytool. In the alternative the tube itself may be made exchangeable foranother with a different tip. The present tool may be used withabrasives such as aluminum oxide or boron-carbide, -of minute particlesizes. Very good results were obtained with abrasives of particle sizein the range of approximately 30 microns. Under operating conditions theabrasive is suspended in a fluid such as water or various oils to formin the working area of the tooth a mud of a consistency which may bequickly varied, for instance by the tools fingertip controls, shown inFig. 5 and hereinafter described. The high frequency and accelerationimpact of the tip motivates the abrasive against the tooth area attackedby it and in the direction pointed by the dentist, as the immediatecause of the tooth excavation. The excavation proceeds at extremelyclose tolerances predetermined by the sizes of the tip and abrasive. Thetip may be made of copper, nickel, iron or other metal suficiently softto permit the abrasive particles to embed themselves loosely in itssurface, to be then by magnetostrictive acceleration propelled againstthe working area of the tooth; or the tip itself may have abrasives suchas diamonds pressed in its surface loosely or in a firm contact. Thetip, when suciently thin as indicated for instance in Figs. 4b and e maybe used as a knife to slice off portions of the tooth laterally.Examples of contra angle types of tips, fiat and edgewise, are shown inFigs. 4b, e and f.

It will be readily appreciated that these contra angle tips make itpossible for the first time in the history of dentistry to drill a toothat any angle required by its usually twisted channels of decay and tofollow them. Up to the present it was necessary to drill away largehealthy portions of the tooth to gain access to the decayed tissues nototherwise accessible by the rotating burr. The contra-angle tips shownalso are able to fill the irregular cavities by their magnetostrictivelycreated impacts. The angle of the end wall 31 and the length of the tip`34 are selected to cooperate in providing optimum access and clinicalworking freedom in the patients mouth. The length of the elongation 34including any working tip attached thereto must be `considered in thedetermination of the length of the tube at the particular frequencyselected. The magnetostriction subjects the tube to lateral andlongitudinal vibrations controlling the multivibrational directions ofthe tip.

Without the abrasive the tool may be used as an impact tool, forinstance to fill an excavated tooth with gold foil. The foil is built upand packed into the cavity as a hardened mass by the continuous impactsof the tool.

The tool makes it possible to employ an unprecedented method of toothfilling with ready made inlays. According to the present invention aninlay of non-brittle material may be used at the end of the tip as thetip itself and will imbed itself into the tooth to be excavated, ifabrasive is applied between it and the tooth. The inlay may be held inplace against the tooth simply by the pressure of the tip, or the toolmay include a conventional grasping mechanism. For instance the inlaymay be held firmly in position on the tooth together with the tools tipwith a jig. The jig may rest on or be clamped to the surrounding teeth.Thus the inlay itself will be countersunk in the tooth to preform therea perfectly fitting cavity for itself with the closest possibletolerance. The inlay itself may be used to excavate the tooth andsimultaneously form its own bed. It will be thereafter taken out, thecavity cleaned and the inlay reinserted and cemented in. Such a methodis possible in a great percentage of tooth fillings. According to thepresent invention the inlays are to be mass produced in severalstandardized sizes corresponding to the most frequently encounteredsizes of cavities to be filled. The inlay may be shaped with a largerbottom than top area, such as a frustated cone or 'pyramid and may bedovetailed into the tooth to anchor it more firmly. An example of suchan inlay is indicated in Fig. 4a showing at the end of tip 34 atriangular prism. A body of any other geometrical shape may be utilizedas an inlay. ,X

An altrenative arrangement is to provide the np 34 itself with a premadeextension of the same predetermined size and shape as an inlay to beinserted into the tooth, of which again Fig. 4a is a demonstration.

In Fig. 6 are shown examples of unconventionally shaped inlays and howthey may be fitted over teeth cavities with the present tool. Fig. 6arepresents a crown 43 which differs from the thin-shelled crowns used upto the present in that it is a combination of a crown and inlay. Theconventional thin-shelled crown must be tailor made individually foreach tooth, and even then its interior does not correspond to thesurface of the tooth and does not repalce the excavated area. A brittlefiller is used to build up the tooth within the shell. Often aircavities remain behind after the crown is cemented on and within a shortinterval the top of the crown, not having a solid support. is bittenthrough and must be replaced. The crown of the present invention shownin Fig. 6a is a solid body having the conventional outer shape and asolid in ner area replacing the excavated tooth portion. Up to presentit would be almost impossible to t a tooth with a premade crown of thistype, since the dentist cannot see inside it, when fitting it over thetooth. It would be also impractical to individually make a crown bodylilling the excavated tooth area. The present invention makes itpossible for the first time to use a premade crown of a standardpredetermined size and shape comprising a solid inner body and an outershell to countersink it over and into the tooth in one simple operation.Fig. 6B shows in front view the example of another type of an inlay 44in the form of a U-shaped band as it tits over a tooth and Fig. 6Cexhibits a side view of a similar inlay with its prong ends sharp andtapered like staples to take a rm grip in the tooths body.

The various conduits of fluid supplies and exhausts may bevalve-controlled by fingertips of the same hand holding the tool duringits operation. Fig. 5 shows the unit 10 provided on the outside ofjacket 16 with valve control knobs 35, 36, 37 slidable by linger tipcontrol, each between a pair of rails 38, 39 and 40. Each conduit isshown provided with a valve; the exhaust with valve 23a, the air linewith valve 29a and the water line with valve 22a, each connected to itsrespective slidable' knob by a control wire 41. Each control wire isprotected by a tubular control wire guide 42. As an example butteryvalves may be used comprising a diaphragm inside the valve housing witha spring loaded shaft controlled by the slidable knob to force thereturn of the valve into its original position upon release.

While magneto-striction has been utilized in the preferred embodiment ofthe invention shown, other sources of high frequency vibrations, such asmechanical, electrical, electromagnetic, piezoelectric or sonic may beemployed as equivalent motive powers of the present dental tool, withoutdeparting from the spirit and scope of the invention.

The alternating current input lines 21 and various iluid conduit linesare admitted into the jacket either through cap 12 or through orificesin the jacket such as 25. The coil 17 is shown in Fig. l cooled throughconduit 24 circulating water through inlet 25, slots 26e and 27 asindicated by arrows, into the interior 28 of tube 13. There the watercools the tube and is dispersed by the magnetostn'ctive motions and bygravity partially through slots (shown in Fig. 2) into the air space 30and partially through hole 32 into the working area 33 to cool the toothunder excavation and to keep the abrasive in liquid suspension. Lines22, 29 and 23 are shown entering the interior of the tube throughorifices in cap 12'. Lines 22, supplying air, and 29, supplying water,extend to the working end 31 of the tube and produce there by combinedfunction and air-water spray penetrating through hole 32 upon theexcavated tooth 33 to cool it. An additional line such as 29, may beincorporated to supply the tooth with the abrasive either dry or insolution with water. An additional vacuum exhaust line such as 23b, maybe extended to the area 33 tovwithdraw excess moisture and used upabrasive from the tooth excavated. The water which penetrates throughslots 15 into the air space 30 and any excess of water in the interior28 of the tube is withdrawn through the vacuum exhaust line 23 whicheliiciently increases the cooling of both the exterior and interiorwalls of the tube.

The advantages of the invention as here outlined are best realized whenall of its features and instrumentalities are combined in the respectivestructures, but useful devices may be produced embodying less than thewhole.

While the tool has been illustrated operable as a dental tool it isby nomeans limited to such purposes, but may be used for instance by artists,in sculpture, diamond setting, in providing artificial dentures withinlays to simulate teeth appearing convincingly true, etc.

It should be understood that the foregoing disclosure relates to only apreferred embodiment of the invention and that it is intended to coverall changes and modifica tions of the examples of the invention hereinchosen for the purposes of the disclosure, which do not constitutedepartures from the spirit and scope of the invention set forth in theappended claims.

I claim:

l. A pencil like shaped dental tool comprising in combi. nation an outerlongitudinal jacket, an inner high frequency oscillating tube suspendedwithin said jacket with a clearance at its working end, and protrudingthrough it at its working end with an extended working tip for endwisefree reciprocating oscillations of said tip, a generator of saidoscillations, a power supply to said generator, and at least one iluidconduit and fluid supply and exhaust means connected with the interiorof said tube.

2. A pencil like shaped dental tool comprising in combination an outercylindrical jacket of magnetic material, an inner tube ofmagnetostrictive material protruding through said jacket at its workingend with an extended working tip, said tube being centered within saidjacket by a sleeve support for otherwise free magnetostrictivemovements, a high frequency magnetostrictive oscillations excitingelectric winding on a spool spaced within said jacket and over saidtube, an alternating current supply exibly connected through the conduitend of said jacket to said winding and two permanent magnet rings, eachmounted inside one end of said jacket and spaced from the adjoininglongitudinal portions of said tube.

3. A pencil like shaped dental tool comprising in combination an outercylindrical jacket of'magnetic material, an inner tube ofmagneto-strictive material protruding through said jacket at its workingend with an extended working tip, said tube being centered within saidjacket by a sleevesupport for otherwise free magneto-strictivemovements, a high frequency magneto-strictiveoscill tions excitingelectric winding on a spool spaced within said jacket and over saidtube, an alternating current supply liexibly connected through theconduit end of said jacket to said winding, two permanent magnet rings,each mounted inside one end of said jacket and spaced from the adjoininglongitudinal portions of said tube, a plu rality of fluid conduits ofabrasive, abrasive suspending medium, and cooling and flushing uid, saidconduits connected with the interior of' said tool for supply andwithdrawal of said iluids, and an end wall at the working end of saidtube provided with a hole connecting the working area of the tool withtheinterior of said tube.

4. A pencil like shaped dental tool comprising in combination an outercylindrical jacket of magnetic material, an inner tube ofmagneto-strictive material protruding through said jacketI at itsworking end with an extended working tip, said tube being centeredwithin said jacket by a sleeve support for otherwise freemagneto-strictive movements with clearance from the ends of the jacketat both ends, a high frequency magneto-strictive oscillations excitingelectric winding on a spool spaced within said jacket and over saidtube, an alternating current supply flexibly connected through theconduit end of said jacket to said winding, two permanent magnet rings,each mounted inside one end of said jacket and spaced from the adjoininglongitudinal portions of said tube, a plurality of uid conduits ofabrasive, abrasive suspending medium, cooling and flushing uids and air,said conduits connected with the interior of said tool for supply andwithdrawal of said uids, an end wall at the working end of said tubeprovided with a hole connecting the working area of the tooth with theinterior of said tube, each of said conduits equipped with fingertipcontrols of said valves mounted on said jacket.

5. A pencil like shaped dental tool comprising in combination an outercylindrical jacket of magnetic materiaL. an inner tube ofmagneto-strictive material protruding through said jacket at its workingend with an extended working tip, said tube being centered within saidjacket by a sleeve support for otherway free magneto-strictivomovements, a high frequency magneto-strictive oscillations excitingwinding on a spool spaced within said jacket and over said tube, analternating current supply flexibly connected through the conduit end ofsaid jacket to said winding, two permanent magnet rings, each mountedinside one end of said jacket and spaced from the adjoining longitudinalportions of said tube, a plurality of uid conduits of abrasive, abrasivesuspending medium, cooling and ushing uid, said conduits connected withthe interior of said tool for supply and withdrawal of said fluids, anengLwall at the working end of said tube provided with a hole connectingthe working area of the tooth with the interior of said tube, each ofsaid conduits equipped with a valve and finger tip control of saidvalves mounted on said jacket, said end wall of said tube being taperedot toward the root of the working tip at an angle of less than 90.

6. In a dental tool, a generator of magneto-strictive oscillationscomprised of a coil member wound upon a spool of non-conductive materialand fiexibly connected to an alternating current supply, and a ux pathconsisting of a jacket member of conductive material concentricallydisposed around said coil, a tubular tool holder element of conductivematerial having a plurality of longitudinal slots concentrically locatedwithin said coil, and a plurality of permanent magnet biasing ringsmounted within said jacket and separated from the tool holder by airgaps; the magnetic bias of the permanent magnet rings, the size of saidair gaps, and the length of the tubular tool holder being deterrninativeof the frequency and amplitude ratings required of the alternatingcurrent supply.

7. In a dental tool, a generator of magneto-strictivc oscillationscomprising a double-layered coil wound upon a spool of non-conductivematerial and flexibly connected to an alternating current supply, a uxpath consisting of a jacket of conductive material concentrically xedabout said coil, a tool holder of conductive tubular material having aplurality of longitudinal slots therein, said tool holder beingconcentrically located within said coil and tixed at its midpoint forsymmetrical oscillations, and a plurality of permanent magnet ringsmounted within said jacket so as to form air gaps between the jacket andtool holder, said permanent magnet rings providing a bias for themagnetic field setup by the coil when it is energized.

References Cited in the le of this patent UNTIED STATES PATENTS1,118,301 Magill Nov.' 24, 1914 1,882,393 Pierce Oct.l l1, 19321,966,446 Hayes July 17, 1934 2,490,273 Kean Dec. 6, 1949

